1. Field of the Invention
The present invention relates to a magnetic head device that includes a reproducing device with a magneto-resistive (MR) head, and in which a piezoelectric element is provided on a supporting member for supporting the MR head, and in particular, to a magnetic head device that prevents the MR head from being broken.
2. Description of the Related Art
FIG. 5 is a plan view of a conventional hard disk drive. A magnetic disk 1 is rotated by a spindle motor 2.
A load beam 4 is joined to an end portion 3a of a carriage having stiffness, and an end portion 4a of the load beam has a slider 5 provided with a flexure (not shown).
The load beam 4 is made of flat spring material. The load beam 4 has a base portion 4b that is fixed to the carriage 3. The end portion 4a of the load beam 4 supports the slider 5.
The slider 5 is provided with a reproducing device that uses magnetically resistive effects to detect a magnetic signal recorded on a magnetic disk 1, and with a recording device that records a magnetic signal on the magnetic disk 1. Airflow, caused by the rotation of the magnetic disk 1, floats the slider 5 above the magnetic disk 1. Recording and reproduction are performed in this floating state.
The carriage 3 has a base portion 3b provided with a voice coil motor 6. The voice coil motor 6 drives the carriage 3 and the load beam 4 in the radial direction of the magnetic disk 1, whereby a seek operation is performed to move the reproducing device and the recording device of the slider 5 onto an arbitrary recording track, and a tracking operation is performed to maintain the reproducing device and the recording device on the central line of the recording track.
As the recording density of the magnetic disk 1 is increased, the precision of the tracking operation must also be increased. Conventionally, the seek operation and the tracking operation are performed such that the voice coil motor 6 only drives the carriage 3.
To increase the precision of the tracking operation, the servo band of a servo system including the voice coil motor 6 must be increased. However, the servo band is limited by a point of mechanical resonance between the carriage 3 and a bearing (not shown) that rotatably supports the carriage 3. The mechanical resonant point of the carriage is determined by the size of the carriage 3, and the size of the carriage 3 is determined by the standard-based diameter of the magnetic disk 1. For example, when the magnetic disk 1 has a diameter of 3.5 inches, the point of resonance between the carriage 3 and the bearing is approximately 3.5 kHz.
When the point of resonance between the carriage 3 and the bearing is approximately 3.5 kHz, then the upper limit of the servo band of the servo system which allows the tracking operation by only driving the carriage 3 by the voice coil motor 6 is approximately 700 Hz.
Accordingly, a method has recently been proposed in which a tracking operation is performed by using a micromotion actuator provided on a load beam to move only an end portion of the load beam.
FIG. 6 is a perspective view of a load beam 11 provided with a piezoelectric element as a micromotion actuator. The load beam 11 is made of a flat-spring stainless-steel material and has a fixed base portion 11a held by a carriage and a moving portion 11b that can be horizontally moved with respect to the fixed base portion 11a. On both sides of a front end portion of the fixed base portion 11a, arm portions 11c extending in the longitudinal direction of the fixed base portion 11a are formed. The moving portion 11b is joined to the arm portions 11c by elastic supporting portions 11d. 
Piezoelectric elements 12 and 13 are provided on the moving portion 11b and the fixed base portion 11a across a gap portion 11e. The piezoelectric elements 12 and 13 are configured such that electrode layers 12a1 and 12a2 are respectively formed on the lower and upper surfaces of a piezoelectric element layer 12b, and electrode layers 13a1 and 13a2 are respectively formed on the lower and upper surfaces of a piezoelectric element layer 13b. 
The load beam 11 in FIG. 6 is connected to a ground (not shown). The electrode layers 12a1 and 13a1 of the piezoelectric elements 12 and 13 are electrically connected to the load beam 11, and are thereby connected to the ground. Each of the piezoelectric layers 12b and 13b of the piezoelectric elements 12 and 13 is polarized in the direction of the layer thickness. The piezoelectric elements 12 and 13 have reverse polarization directions. Therefore, when the same potential is applied to the electrode layers 12a2 and 13a2, one piezoelectric element extends longitudinally, while the other piezoelectric element contracts longitudinally.
As a result, the elastic supporting portions 11d warp to change the posture of a slider 21 provided on an end portion of the moving portion 11b. In other words, by moving the slider 21 in a track-width direction, a tracking operation can be performed. By using a piezoelectric-element-mounted load beam to form a servo system, the servo band can be set to 2 kHz or greater.
The piezoelectric elements 12 and 13 are warped when a voltage is applied through conductor 14 to the electrode layers 12a1, 12a2, 13a1, and 13a2. Conversely, when the piezoelectric elements 12 and 13 are warped due to stress, a voltage is generated between the electrode layers 12a1 and 12a2 and a voltage is generated between the electrode layers 13a1 and 13a2.
In particular, when touching some conductor, surge current may flow in the piezoelectric elements 12 and 13 because, in the process for ultrasonically cleaning or carrying the magnetic head device, large vibrations may act on the piezoelectric elements 12 and 13. The surge current may reach a frequency of several hundred to several thousand megahertz and a magnitude of several amperes. This high frequency current causes an adjacent conductive pattern to generate an induced current. Also, a change in the voltage of the high frequency causes capacitive coupling with the conductive pattern, so that the current is transferred. In particular, when the magnetic head device is cleaned, current transfer occurs due to capacitive coupling caused by water having a dielectric constant several ten times that of air.
In particular, the reproducing device is often broken by the above current in the supersonic cleaning or carrying process since it has low durability against the above current.
Accordingly, it is an object of the present invention to provide a magnetic head device that reduces damage to a reproducing device and a recording device in a structure having a recording conductive pattern for transmitting a recording signal, and which comprises a control conductive pattern that supplies a control signal to a piezoelectric element connected thereto, and a reproducing conductive pattern that transmits a signal obtained by reproduction.
To this end, and according to the present invention, there is provided a magnetic head device including a slider provided with a reproducing device for using magnetoresistance to detect a magnetic signal recorded on a recording medium, and a recording device for recording a magnetic signal on the recording medium, a wiring member having a reproducing conductive pattern connected to the reproducing device and a recording conductive pattern connected to the recording device, and an elastic supporting member for supporting the slider and the wiring member. A piezoelectric element for changing the posture of the slider by warping the elastic supporting member is provided on the elastic supporting member, and the recording conductive pattern is formed between the reproducing conductive pattern and a control conductive pattern that is formed on the wiring member and which supplies a control signal to the piezoelectric element connected thereto.
Preferably, pads are formed at ends of the reproducing pattern and the recording conductive pattern that are opposite to the other ends respectively connected to the reproducing device and the recording device, and a pad is formed at one end of the control conductive pattern that is opposite to the other end connected to the piezoelectric element.
The elastic supporting member may be connected to the ground by a conductive material, and the ground terminal of the piezoelectric element may be connected to the ground by the elastic supporting member.
The control conductive pattern may include a grounding pattern to which the ground terminal of the piezoelectric element is connected and a control signal pattern that is connected to a terminal other than the ground terminal of the piezoelectric element and which supplies a control signal.
Among the pads formed at the ends of the reproducing conductive pattern, the recording conductive pattern, and the control conductive pattern, the pad formed at the end of the control conductive pattern may be closest in position to the piezoelectric element.
According to the present invention, a recording conductive pattern is formed between a control conductive pattern and a reproducing conductive pattern. This can reduce the capacitance between the control conductive pattern and the reproducing conductive pattern.
Accordingly, in a process for ultrasonically cleaning or carrying a magnetic head device, when a surge current flows from a piezoelectric element to the control conductive pattern, the capacitive coupling between the control conductive pattern and the reproducing conductive pattern can be reduced, whereby the flow of a current in the reproducing conductive pattern can be prevented and damage to a reproducing device having low durability can be reduced.